How conductive is plastic

Korean scientists succeeded for the first time in producing a polymer in such a way that it behaves like a classic metal even at low temperatures.

Busan (Korea) - Without plastic that conducts electricity well, cheap radio chips, printed circuits and flexible screens are unthinkable. Plastics mixed with metals and polyaniline offer promising conductivity, but lag far behind copper or silver.

"The use of such high-performance semiconducting and metallic polymers for 'plastic electronics' will significantly expand the range of possible applications," said Kwanghee Lee and his colleagues from Pusan ‚Äč‚ÄčNational University in Busan. The researchers present their results, which could lead to numerous new products, in the journal "Nature".

While the electrical resistance of plastics used to increase with decreasing temperature, the new polyaniline layers turn this behavior on its head. Just as with a metal, the electrical resistance also drops when the material is cooled to around minus 268 degrees Celsius with liquid helium. At room temperature, the specially structured polyaniline has a conductivity of around 1000 Siemens per centimeter. When cooled, this value more than doubles.

Lee's team sees the reason for this in the improved mobility of the electrons. This was achieved through the optimized manufacturing process. To do this, the researchers distributed the long molecular chains in oily drops in water. When an acid was added, the conductive macromolecules were arranged in extremely thin films in such a way that the electrons could be passed on from chain to chain better and better, even at low temperatures. The new material even showed the reflection behavior of light typical of metals, but only in the infrared range. Although this demonstration of true metallic behavior can be considered a breakthrough for polymer electronics, it also shows the limits of conductive plastics. Even with this optimized production process, the conductivity remains around two orders of magnitude below that of copper.